Micro-prober for wafer-level low-noise measurements in MOS devices

Low-frequency noise measurements represent an interesting investigation technique for the characterization of the quality and reliability of microelectronic materials and devices. Performing meaningful noise measurements at low and very low (f<1 Hz) frequencies, however, may be quite challenging, particularly because of the many sources of interference that superimpose on the noise signal. For this reason, packaged samples are preferred because they allow accurate shielding from the external environment, and because keeping the sample in close proximity to the low-noise biasing system and amplifier reduces microphonic and electromagnetic disturbances. Notwithstanding this, the possibility of performing low-frequency noise measurements at wafer level would be quite interesting, both because of the ease of obtaining wafer-level samples from industries with respect to packaged samples, and because this would avoid possible packaging-process induced device degradation. The purpose of this work is to demonstrate that it is, in fact, possible to design and build a dedicated probe system for performing high-sensitivity, low-frequency noise measurements on metal-oxide-semiconductor devices at wafer level.     

Evaluating k-values for low-k materials after damascene integration: Method and results

This work discusses a method for measuring k-values of low-k films after integration in damascene structures. The experimental results are obtained from 90 nm ½ pitch single damascene structures on low-k materials with intrinsic k-values ranging between 2.2 and 3. The measurement technique is discussed in detail with a focus on the accuracy, limitation of the method, impact of low-k damage and applicability for smaller dimensions.     

How to enlarge the bandwidth without increasing the noise in OP-AMP-based transimpedance amplifier

Increasing the bandwidth without degrading the noise performance represents the main challenge in the design of transimpedance amplifiers. This paper presents a novel circuit topology for a transimpedance amplifier that allows obtaining an improved tradeoff between equivalent input noise and bandwidth with respect to the conventional approach. The effectiveness of the new topology has been demonstrated by designing and testing a prototype of a transimpedance amplifier based on the proposed topology.     

Characterization of Al-Si-Cu metal lines by means of tem analysis and the sarf technique

Four groups of samples deposited at different temperatures, T_D, have been characterized by means of the SARF (Spectral Analysis of Resistance Fluctuations) technique. For each temperature, lines with the same length (800 μm) and two different widths (1 μm and 2 μm) were available. An accurate TEM (Transmission Electron Microscopy) analysis has been carried out with the aim of investigating the dependence of the microstructure on T_D. While 1-μm-wide lines showed a quasi-bamboo structure, regardless of T_D, 2-μm-wide lines appeared constituted by grains whose size was smaller than the stripe width. In this case, the grain size distribution was dependent on T_D. A new microstructural parameter has been introduced to which electromigration noise seems to be very sensitive: the percentage of grains of the metal film whose size is smaller than the stripe width. The correlation observed among noise parameters, microstructural characteristics of the lines and, in the case in which they were available, lifetime data, has confirmed the potentiality of the SARF technique as a diagnostic tool.     

A new correlation method for high sensitivity current noise measurements

The properties of a differential transconductance amplifier coupled with a four channel measurement system are exploited in order to reach a very high sensitivity in current noise measurements. In particular, it is demonstrated that, in proper conditions, the noise contributions coming from the active and passive devices that make up the transresistance amplifier can be virtually eliminated. Moreover, the proposed measurement method allows the evaluation of the impedance of the device under test from noise measurement data. Actual measurement results are also reported that demonstrate the effectiveness of the proposed approach.     

Copper interconnection lines: SARF characterization and lifetime test

Copper thin films have been deposited onto silicon substrates by means of two different deposition techniques, resulting in metallizations with different microstructure. In particular, transmission electron microscopy (TEM) observations have shown that the two types of films are characterized by different distributions of the grain size. Lifetime and SARF (Spectral Analysis of Resistance Fluctuations) tests have been performed on lines obtained from the two metallizations in order to compare their resistance to electromigration. The results of the tests confirm those already obtained in A1 based lines; in fact, a clear correlation exists among the average grain size, the lifetime and the level of electromigration noise.     

Wafer level measurement system for sarf characterization of metal lines

A feasibility study concerning the application of the SARF technique at wafer level has been performed. The main problem of this type of measurements is the excess noise generated at the point contacts used to supply the lines under investigation with the test current. This problem has been successfully solved by setting up a probe station entirely contained in a shielded box and by supplying the samples under test by means of purposely designed low noise current sources. The background noise of the whole measurement system coincides with that of the system used until now for packaged samples.     

Simulation and Measurement of Shot Noise in Resonant Tunneling Structures

We present numerical simulations and measurements of shot noise in resonant tunneling structures. We show that when electron-electron interaction through Coulomb force and Pauli exclusion is properly taken into account, the main features of noise behavior of such devices can be correctly predicted. Electron-electron interaction is shown to be responsible for the suppression of shot noise in the positive differential resistance region of the I-V curve, and for the enhancement of shot noise in the negative differential resistance region.